1. Technical Field
This invention pertains to seals in general and to brush seals in particular.
2. Background Information
Brush seals comprising a plurality of bristles sandwiched between a facing plate and a backing plate may be used to prevent or inhibit fluid flow from a higher pressure region to a lower pressure region. Typically, the brush seal seals the gap between a stationary member and a rotating member where the higher pressure region exists on one side of the members and the low pressure region on the other side. The seal is attached to either the stationary or the rotating member with its bristles extending across the gap therebetween. The bristles are usually positioned out of contact with the sealing surface section of the other of the stationary or rotating member under ambient conditions. Under higher temperatures, the bristles may contact the sealing surface section of the other of the stationary or rotating member if sufficient thermal expansion has occurred. Moreover, under extreme thermal conditions it is possible for the backing plate of the seal to thermally expand and contact the sealing surface. In all cases, contact between the seal and the sealing surface can cause undesirable wear and may even necessitate replacement of the stationary or rotating member having the sealing surface.